Particulate materials

ABSTRACT

Embodiments of the invention relate to particles of active substances, methods for preparing the particles, formulations containing the particles, and metered dose inhalers containing such particles or formulations. In one embodiment, a composition of an aerosol formulation is provided and contains a particulate active substance of non-micronized, solid particles having a mass median aerodynamic diameter of less than 10 μm suspended in a hydrofluorocarbon fluid vehicle at a concentration within a range from about 0.2% w/v to about 5% w/v. The aerosol formulation exhibits a flocculation volume of about 85% or greater about 1 minute after mixing the particulate active substance and the hydrofluorocarbon fluid vehicle. The particulate active substance contains an alkaloid ergotamine, pharmaceutically acceptable salts thereof, analogues thereof, or derivatives thereof. In some examples, the alkaloid ergotamine contains dihydroergotamine, such as dihydroergotamine mesylate and the hydrofluorocarbon fluid vehicle contains HFA 134a, HFA 227ea, or mixtures thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/448,271, filed Mar. 2, 2017, now allowed, which is a continuation ofU.S. application Ser. No. 14/451,201, filed Aug. 4, 2014, now U.S. Pat.No. 9,616,060, which is a continuation of U.S. application Ser. No.13/908,540, filed Jun. 3, 2013, now U.S. Pat. No. 8,828,359, which is acontinuation of U.S. application Ser. No. 13/294,881, filed Nov. 11,2011, now U.S. Pat. No. 8,470,301, which is a continuation of U.S.application Ser. No. 12/483,378, filed Jun. 12, 2009, now U.S. Pat. No.8,080,236, which is a continuation of U.S. application Ser. No.10/413,457, filed Apr. 14, 2003, now U.S. Pat. No. 7,582,284, whichclaims priority to GB 0209402.7, filed Apr. 23, 2002, and to GB0208742.7, filed Apr. 17, 2002, all of which are incorporated byreference herewith in their entireties.

FIELD OF THE INVENTION

Embodiments of the invention relate to particles of active substances,methods for preparing the particles, formulations containing theparticles, and metered dose inhalers containing the particles orformulations.

BACKGROUND TO THE INVENTION

Certain pharmaceuticals may be delivered to the nose and/or lungs of apatient by inhalation, using an inhaler device of which there areseveral known types. In some of these devices, the drug (or aformulation containing the drug, for instance together with apharmaceutically acceptable excipient such as lactose) is suspended inparticulate form in a fluid vehicle, which acts to transport the drug ina suitably disperse state towards the intended site of administration.The vehicle may be a pressurized propellant fluid if the drug is to bedelivered in aerosolized form. “Metered dose inhalers” (MDIs) may forexample be used to effect such delivery, for instance those used todispense budesonide (Pulmicort™, AstraZeneca), salbutamol (Ventolin™,Glaxo SmithKline and Proventil HFA, Schering Plough), salmeterolxinafoate (Serevent™, Glaxo SmithKline) and fluticasone (Flovent™, GlaxoSmithKline)

Typical propellant fluids include hydrofluoroalkanes such as1,1,1,2-tetrafluoroethane (available as HFA 134a),1,1,1,2,3,3,3-heptafluoropropane (available as HFA 227ea) and1,1,2,2,3-pentafluoropropane.

The particulate drug must be suspended as uniformly as possible in thefluid vehicle. This is usually achieved by shaking the inhalation deviceprior to dispensing a dose of the drug. It is clearly desirable that thedrug remains suspended in the vehicle for a sufficient length of timeafter shaking to allow it to reach the intended site of administration.However, particulate drug/propellant suspensions tend only to be stablefor limited periods of time. Where the drug is denser than thepropellant, the tendency is for it to “settle” or “flocculate”, i.e., tofall out of suspension. Where it is less dense than the propellant, thedrug tends to “cream” or float towards the top of the propellant volume.This can reduce the efficiency and therefore also accuracy of drugdosage delivery. Often dispersion enhancing agents such as surfactantsneed to be added to the drug/propellant mixture to achieve and sustain asuitably uniform suspension.

Even using such techniques, it has typically proved difficult to prepareinhalable suspensions which are stable during normal storage periods andconditions and which give uniform dosing throughout the useful life ofthe average inhaler.

It has also been proposed to use hollow, or at least partially fluidcontaining, particles in MDI formulations in order to obtain improveddispersibility—see for instance the perforated microstructures describedin U.S. Pat. No. 6,309,623 and the hollow microspheres disclosed inWO-97/36574, both suggested for use in inhalers.

Particulate active substances, such as drugs, may be produced by avariety of known methods, including for example crystallization fromsolution, anti-solvent precipitation from solution, milling,micronization, spray drying, freeze drying or combinations of suchprocesses. Also known are particle formation processes which make use ofsupercritical or near-critical fluids, either as solvents for thesubstance of interest—as in the process known as RESS (Rapid Expansionof Supercritical Solution—see Tom & Debenedetti, J. Aerosol. Sci., 22(5), 555-584 (1991))—or as anti-solvents to cause the substance toprecipitate from another solution—as in the process known as GAS (GasAnti-Solvent) precipitation (see Gallagher et al., ACS Symp. Ser., 406,p. 334 (1989)).

In general, however, known processes for producing inhalable drugs yieldparticles which perform poorly in propellant fluids, i.e., they exhibitpoor flocculation behavior. For many known particulate drugs, thetendency to flocculate can be a severe problem, with significantsettling occurring within less than a minute of shaking the suspensionand thus often before a dose of the drug has been successfully dispensedor at least before it has reached its target site of administration.

It would therefore be desirable to provide particulate drugs, and indeedother active substances which may need to be delivered in suspension influid vehicles, which have improved flocculation behavior in suchvehicles.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is providedan active substance in particulate form, which is insoluble in the fluidvehicle 1,1,1,2-tetrafluoroethane (HFA 134a) and which when suspended inthat vehicle, at a concentration of from 0.2 to 5% w/v, exhibits aflocculation volume of 35% or greater after 5 minutes.

According to a second aspect, the invention provides an active substancein particulate form, which is insoluble in the fluid vehicle1,1,1,2,3,3,3-heptafluoropropane (HFA 227ea) and which when suspended inthat vehicle, at a concentration of from 0.2 to 5% w/v, exhibits aflocculation volume of 35% or greater after 5 minutes.

A third aspect of the present invention provides an active substance inparticulate form, which is insoluble in the fluid vehicle1,1,1,2-tetrafluoroethane (HFA 134a) and which when suspended in thatvehicle at a concentration of from 0.2 to 5% w/v exhibits a flocculationvolume after 5 minutes which is at least 20% higher, preferably at least50% or 150% or 200% or 250% higher, than that exhibited by the samechemical entity having the same or a similar particle size (typicallymeasured MMAD, “similar” here meaning within 80 to 120%, preferablywithin 90 to 110%, of the measured MMAD) but prepared using amicronization process.

A fourth aspect provides an active substance in particulate form, whichis insoluble in the fluid vehicle 1,1,1,2,3,3,3-heptafluoropropane (HFA227ea) and which when suspended in that vehicle at a concentration offrom 0.2 to 5% w/v exhibits a flocculation volume after 5 minutes whichis at least 20% higher, preferably at least 50% or 150% or 200% or 250%higher, than that exhibited by the same chemical entity having the sameor a similar particle size (as described above) but prepared using amicronization process.

A fifth aspect of the present invention provides an active substance inparticulate form, which is insoluble in the fluid vehicle1,1,1,2-tetrafluoroethane (HFA 134a) and which when suspended in thatvehicle at a concentration of from 0.2 to 5% w/v exhibits a rate ofchange (decrease) in flocculation volume, during the first 60 secondsafter thorough mixing of the active substance and vehicle, of 20% perminute or less.

A sixth aspect provides an active substance in particulate form, whichis insoluble in the fluid vehicle 1,1,1,2,3,3,3-heptafluoropropane (HFA227ea) and which when suspended in that vehicle at a concentration offrom 0.2 to 5% w/v exhibits a rate of change (decrease) in flocculationvolume, during the first 60 seconds after thorough mixing of the activesubstance and vehicle, of 20% per minute or less.

A seventh aspect of the present invention provides the use of asupercritical fluid processing method to produce an active substance inparticulate form, for the purpose of improving the flocculationperformance of the substance.

According to an eighth aspect of the present invention, there isprovided an active substance for use in a method of surgery, therapy ordiagnosis practiced on a human or animal body, in which method thesubstance is delivered to a patient in suspension in a nonsolvent fluidvehicle in which the flocculation performance of the substance is asdefined above in relation to any one of the first to the sixth aspectsof the invention.

A ninth aspect of the invention provides the use of an active substancein the manufacture of a medicament which comprises a suspension of thatsubstance in a nonsolvent fluid vehicle, in which suspension theflocculation performance of the active substance is as defined above inrelation to any one of the first to the sixth aspects of the invention.The medicament may be for use in a method of surgery, therapy ordiagnosis practiced on a human or animal body, and is preferablysuitable for delivery by inhalation.

A tenth aspect provides the use of an active substance according to anyone of the first to the sixth aspects, in suspension in a nonsolventfluid vehicle at a concentration of at least 0.2% w/v, preferably atleast 0.5% w/v, and more preferably the suspension containing no, orless than 0.1% w/w based on the weight of the active substance,preferably less than 0.01% w/w or less than 0.001 or 0.0001% w/w,dispersion enhancing or stabilizing additives such as surfactants. Thesuspension preferably contains no co-solvents or lubricity enhancingadditives.

An eleventh aspect of the invention provides a formulation, typically anaerosol formulation, containing an active substance according to any oneof the first to the sixth aspects suspended in a nonsolvent fluidvehicle. Aerosol formulations according to this aspect typicallycomprise a fine particle fraction of at least 25%, preferably at least30%, most preferably at least 35%.

A twelfth aspect of the present invention provides a drug deliverydevice, preferably an inhaler, which contains one or more dosageformulations of an active substance according to any one of the first tothe sixth aspects, and preferably also a suitable fluid vehicle in whichto aerosolize the substance. Alternatively, the delivery device maycontain, or be able to produce, one or more aerosol formulationsaccording to the eleventh aspect of the invention. The delivery deviceis preferably of the type designed to deliver a predetermined dose of anactive substance in a pressurized fluid vehicle, for instance a metereddose inhaler (which term includes pressurized metered dose inhalers(pMDIs)).

A thirteenth aspect of the invention provides an aerosol can containingan aerosol formulation according to the eleventh aspect of theinvention, and which is suitable for use in a delivery device such as aMDI, preferably a device according to the twelfth aspect of theinvention.

According to a fourteenth aspect, the invention provides a method fordelivering an active substance, the method involving charging an aerosolcan with an active substance and/or a formulation according to theinvention. Subsequent delivery of the can contents may be via a deliverydevice such as a MDI.

A fifteenth aspect provides a method of treatment of a human or animalpatient, which method involves administering to the patient, preferablyusing a method according to the fourteenth aspect of the invention, anactive substance and/or a formulation according to the invention.

These and other aspects of the invention will be readily apparent inview of the detailed discussion and examples below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the time variation in flocculation volume of threesamples made according to the present invention in HFA 134a, expressedas a percentage of the initial volume.

FIG. 2 depicts the time variation in flocculation volume of threesamples made according to the present invention in HFA 227ea, expressedas a percentage of the initial volume.

FIG. 3 depicts the time variation in flocculation volume of budesonidesamples made according to the present invention in HFA 134a, expressedas a percentage of the initial volume.

FIG. 4 depicts the time variation in flocculation volume of budesonidesamples made according to the present invention in HFA 227ea, expressedas a percentage of the initial volume.

FIG. 5 is a plot depicting the changes in flocculation volume ofparticulates in HFA 134a made according to the invention over a 10minute period, expressed as a percentage of the initial volume.

FIG. 6 is a plot depicting the changes in flocculation volume ofparticulates in HFA 227ea made according to the invention over a 10minute period, expressed as a percentage of the initial volume.

FIG. 7 is a plot depicting the changes in flocculation volume ofparticulates in HFA 134a made according to the invention over a 10minute period, expressed as a percentage of the initial volume.

FIG. 8 is a plot depicting the changes in flocculation volume ofparticulates in HFA 227ea made according to the invention over a 10minute period, expressed as a percentage of the initial volume.

FIG. 9 is a plot depicting the changes in flocculation volume of DHEparticulates in HFA 227ea made according to the invention.

FIG. 10 is a plot depicting the changes in flocculation volume ofparticulates in HFA 134a made according to the invention.

FIG. 11 is a plot depicting the changes in flocculation volume ofparticulates in HFA 227ea made according to the invention.

FIG. 12 is a plot depicting the changes in flocculation volume ofparticulates in HFA 134a made according to the invention.

FIG. 13 is a plot depicting the changes in flocculation volume ofparticulates in HFA 227ea made according to the invention.

DETAILED DESCRIPTION

Flocculation volume, as referred to herein, is a measure of the amountof the vehicle which is occupied by the particulate suspension; a highervalue therefore indicates less flocculation (in the case where theactive substance is denser than the vehicle) or less creaming (in thecase where the active substance is less dense than the vehicle), andaccordingly improved performance due to the more uniform dispersion ofthe solid in the vehicle.

For the purpose of defining the present invention, the vehicles HFA 134aand HFA 227ea are referred to as suitable reference standards in whichto measure flocculation volume. An active substance according to theinvention may, however, be used in suspension in any suitable nonsolventvehicle to give improved flocculation performance.

According to the first and/or second aspects of the invention, theflocculation volume after 5 minutes is preferably 40% or greater, morepreferably 50% or greater, still more preferably at least 60% or 70% or75% or 80% or 85% or 90% or 95% or 98%. The figure achieved may dependon the nature of the active substance, and factors such as its particlesize and morphology, as described below.

This flocculation volume is preferably exhibited after 6 minutes, morepreferably after 8 minutes, still more preferably after 10 minutes, mostpreferably after 15, 30 or 60 minutes or in some cases after 2, 6, 12 oreven 24 hours. It is certainly exhibited after only 0.5 or 1 or 2minutes. The flocculation volume is preferably measured at aconcentration of above 0.5% w/v, more preferably from 0.5 to 3 or 4%w/v, most preferably from 0.5 to 1.5 or 2% w/v or from 0.8 to 1.3 or1.5% w/v, such as 1% w/v. The above described flocculation performancemay also be exhibited at lower active substance concentrations, forinstance down to 0.15 or even 0.1% w/v.

The flocculation volume is preferably greater than 50% after 20 seconds,more preferably after 30 or 40 or 60 or 90 seconds, most preferablyafter 2 or 3 or even 5 minutes.

The active substances of the invention preferably exhibit the abovedescribed flocculation performance in other nonsolvent fluid vehicles,in particular hydrofluorocarbon propellants or mixtures thereof (forexample, in a mixture of HFA 134a and HFA 227ea).

Preferably the active substances of the invention exhibit the abovedescribed flocculation behavior in the absence of dispersion enhancingor stabilizing additives (e.g., surfactants) in the activesubstance/vehicle mixture, or at least at lower levels of such additivesthan have previously been necessary for the same activesubstance/vehicle pair, for instance at additive (in particularsurfactant) levels of less than 0.1% w/w based on the weight of theactive substance, preferably less than 0.01% w/w or less than 0.001 or0.0001% w/w.

They preferably exhibit this flocculation behavior in the absence ofco-solvents, in particular polar co-solvents such as alcohols (e.g.,ethanol).

Thus, their flocculation volumes are preferably measured in suspensionscontaining only, or consisting essentially of, the active substance andthe relevant vehicle.

Further, the active substances of the invention preferably exhibit theabove described behavior in the absence of (or at low levels of, such asless than 0.1 or 0.01 or 0.001% w/v based on the total suspensionvolume) lubricity enhancing additives, either in the activesubstance/vehicle mixture or on the internal surfaces of the containerin which the flocculation performance of the mixture is tested. Typicalsuch lubricants which are currently used in aerosol formulations includepolyvinyl pyrrolidones and polyethylene glycols; coatings which areoften used on the surfaces of for example aerosol canisters includeepoxy resins or phenolic vinyl type coatings.

Thus, the flocculation volume of the active substance in the vehicle maybe measured in a container made of for example glass or aluminum, theinternal surfaces of which need not carry or incorporate any lubricityenhancing materials.

The mass median diameter (MMD) of the active substance particles ispreferably less than 15 μm or in particular less than 10 μm, morepreferably less than 5 or 4 μm, most preferably less than 3.5 or 3.3 or3 or 2 or even 1 μm. It may be greater than 1 or 2 or even 2.5 μm. Themass median aerodynamic diameter (MMAD) of the active substanceparticles is preferably less than 10 microns, more preferably less than5 microns, and most preferably less than 3.5 microns. For a givenparticle size, active substances according to the invention candemonstrate significantly better flocculation performance than thecorresponding chemical entities made by conventional techniques such asspray drying, freeze drying and in particular micronization.

Particle sizes may be measured for instance using (a) an AEROSIZER™time-of-flight instrument (which gives an aerodynamic equivalentparticle diameter, MMAD) or (b) a laser diffraction sensor such as theHELOS™ system available from SYMPATEC™ GmbH, Germany (which provides ageometric projection equivalent MMD). MMADs may also be assessed using acascade impactor. Volume mean diameters may be obtained in both casesusing commercially available software packages. Active substancesaccording to the present invention preferably have a volume-weightedmedian aerodynamic diameter (VMAD, measured for instance by laserdiffraction analysis) of 5 μm or less, more preferably of 4 μm or 3.5 μmor less.

The active substances of the invention are preferably in the form ofsolid (e.g., as opposed to hollow, porous (which includes perforated) orat least partially fluid-containing) particles. They are preferably,although not necessarily, in a crystalline or semi-crystalline (asopposed to amorphous) form. More preferably they are crystalline,ideally highly crystalline, since the crystalline form of a material isoften more stable in suspension than its amorphous or partiallycrystalline forms which may more readily dissolve in the fluid vehicle,with a risk of re-crystallization and/or particle growth.

An active substance according to the invention is thus preferably from80% to 100% or from 90% to 100%, ideally 100% crystalline. It maytherefore contain less than 20% w/w, preferably less than 10% w/w, morepreferably less than 5 or 2 or 1 or even 0.5% w/w, most preferably no,detectable amorphous phase regions.

Crystallinity may be assessed in known ways for instance using X-raydiffraction (XRD) techniques, preferably high resolution X-ray powderdiffraction such as using a synchrotron radiation source. Degree ofcrystallinity may be assessed for instance with respect to crystals ofthe same chemical entity produced by slow evaporative crystallizationfrom solution. X-ray diffraction line broadening can provide anindication of reduced crystallinity, for example of crystal latticeimperfections. Line broadening may be manifested for instance by anincreased peak width (e.g., full width at half maximum height, FWHM) forone or more of the diffraction peaks. A reduced level of crystal latticeimperfections, in a particulate product according to the invention, mayalso be manifested by a shift in position, towards higher 28 values(typically a shift of 0.0005° or more, such as of from 0.0005° to 0.005°or from 0.001° to 0.003°), of one or more of the X-ray diffractionpeaks, for instance compared to particles of the same chemical entityproduced by micronization.

Levels of amorphous and crystalline phases, in an active substanceaccording to the invention, may also be assessed by reference to itsmoisture uptake at any given temperature and humidity, and/or itsthermal activity profile, again in known ways.

An active substance according to the invention preferably has anacicular crystalline form, i.e., a crystalline form which issignificantly longer in one dimension than in at least one otherdimension; this embraces for example needle-like crystals and also,potentially, wafer-, blade- or plate-like crystals (which aresignificantly longer in two dimensions than in the third) and elongateprism-shaped crystals. These have in cases been found to show betterflocculation performance than similarly sized (e.g., with the samemeasured MMAD, or within 80% to 120% of the measured MMAD) particles ofother shapes. Needle-like crystals may be preferred for theirflocculation performance, and in this case the mass median particlediameter may be greater than 3 or 4 or 5 μm, perhaps greater than 6 or 7or 8 or even 10 μm, although preferably (especially for delivery byinhalation) it will be 6 μm or less, more preferably 5 μm or less.Plate- or blade-like particles may be preferred for use in inhalers, andmay have a mass median particle diameter of greater than 3 or 4 or 5 or6 μm, although again for inhalation a preferred diameter may be 6 μm orless, more preferably 5 μm or less.

In the above discussion, “significantly” longer means at least 5%,preferably at least 10% or 20% or 30%, greater than the lower of the twodimensions being compared. Particles of an active substance according tothe present invention preferably have an aspect ratio (the ratio of thelongest to the shortest particle dimension) of 2:1 or greater, morepreferably 3:1 or 4:1 or greater, most preferably from 1.5:1 to 5:1 orfrom 2:1 to 4.5:1.

The active substance is preferably in a substantially (e.g., 95% w/w orgreater, preferably 98% or 99% w/w or 99.5% w/w or greater) pure form.It preferably contains low levels of residual solvent, for example lessthan 500 ppm, more preferably less than 200 ppm, most preferably lessthan 150 or 100 ppm residual solvent, by which is meant solvent(s) whichwere present at the point of particle formation. Still more preferablythe substance contains no detectable residual solvent, or at least onlylevels below the relevant quantification limit(s). It is believed thatlower residual solvent levels help to stabilize the particles in fluidsuspensions, in particular in the presence of moisture, reducing thetendency for amorphous phase regions to re-crystallize and hence forparticle growth and agglomeration.

If the active substance is a substance capable of existing in two ormore different polymorphic forms, it preferably consists of only onesuch form, with a purity of 99.5% w/w or greater, preferably of 99.8%w/w or greater, with respect to the other polymorphic form(s).Polymorphic purity may be assessed for instance using melting point data(e.g., differential scanning calorimetry) or more preferably using X-raypowder diffraction (for instance the small-angle X-ray scattering (SAXS)technique) to detect polymorphic transitions during heating, based onthe diffraction peaks characteristic of the polymorphs.

By “active substance” in the present context is meant a substancecapable of performing some useful function in an end product, such aspharmaceutical or pesticidal substances.

The active substance may be a single active substance or a mixture oftwo or more. It may be monomeric, oligomeric or polymeric, organic(including organometallic) or inorganic, hydrophilic or hydrophobic,polar or non-polar. It may be a small molecule, for instance a syntheticdrug like paracetamol, or a macromolecule such as a protein or peptide(including enzymes, hormones, antibodies and antigens), nucleotide,nucleoside or nucleic acid. Other potential active substances includevitamins, amino acids, lipids including phospholipids and aminolipids,carbohydrates such as mono-, di-, oligo- or polysaccharides, cells andviruses.

The active substance preferably comprises (more preferably is) apharmaceutically or nutraceutically active substance, or apharmaceutically or nutraceutically acceptable excipient, or a mixtureof two or more thereof. More preferably the active substance is apharmaceutically active substance which is suitable for delivery byinhalation (which term includes nasal and/or oral inhalation), whetherfor local administration (e.g., an asthma drug intended for localdelivery to the lung) or for systemic delivery via the lung. Howevermany other active substances, whatever their intended functio (forinstance, herbicides, pesticides, foodstuffs, imaging agents, dyes,perfumes, cosmetics and toiletries, detergents, coatings, products foruse in the ceramics, photographic or explosives industries, etc.) areembraced by the present invention.

Of particular interest for delivery by inhalation (ideally using metereddose inhalers) are pharmaceutically active substances which need to bedelivered systemically and require rapid onset of action. According to apreferred embodiment, formulations are provided which achieve a maximumconcentration of a pharmaceutically active substance, C_(max), within 1hour of administration, preferably within 30 minutes, and mostpreferably within 15 minutes. This time to achieve maximum concentrationof the active substance is referred to herein as T_(max).

Examples of pharmaceutically active substances which may be delivered byinhalation include β2-agonists, steroids such as glucocorticosteroids(preferably anti-inflammatories), anti-cholinergics, leukotrieneantagonists, leukotriene synthesis inhibitors, pain relief drugsgenerally such as analgesics and anti-inflammatories (including bothsteroidal and non-steroidal anti-inflammatories), cardiovascular agentssuch as cardiac glycosides, respiratory drugs, anti-asthma agents,bronchodilators, anti-cancer agents, alkaloids (e.g., ergot alkaloids)or triptans such as sumatriptan or rizatriptan that can be used in thetreatment of migraine, drugs (for instance sulphonyl ureas) useful inthe treatment of diabetes and related disorders, sleep inducing drugsincluding sedatives and hypnotics, psychic energizers, appetitesuppressants, anti-arthritics, anti-malarials, anti-epileptics,anti-thrombotics, anti-hypertensives, anti-arrhythmics, anti-oxicants,anti-depressants, anti-psychotics, anxiolytics, anti-convulsants,anti-emetics, anti-infectives, anti-histamines, anti-fungal andanti-viral agents, drugs for the treatment of neurological disorderssuch as Parkinson's disease (dopamine antagonists), drugs for thetreatment of alcoholism and other forms of addiction, drugs such asvasodilators for use in the treatment of erectile dysfunction, musclerelaxants, muscle contractants, opioids, stimulants, tranquilizers,antibiotics such as macrolides, aminoglycosides, fluoroquinolones andbeta-lactams, vaccines, cytokines, growth factors, hormonal agentsincluding contraceptives, sympathomimetics, diuretics, lipid regulatingagents, antiandrogenic agents, antiparasitics, anticoagulants,neoplastics, antineoplastics, hypoglycemics, nutritional agents andsupplements, growth supplements, antienteritis agents, vaccines,antibodies, diagnostic agents, and contrasting agents and mixtures ofthe above (for example the asthma combination treatment containing bothsteroid and p-agonist).

More particularly, the active agent may fall into one of a number ofstructural classes, including but not limited to small molecules(preferably insoluble small molecules), peptides, polypeptides,proteins, polysaccharides, steroids, nucleotides, oligonucleotides,polynucleotides, fats, electrolytes, and the like.

Specific examples include the β2-agonists salbutamol (e.g., salbutamolsulphate) and salmeterol (e.g., salmeterol xinafoate), the steroidsbudesonide and fluticasone (e.g., fluticasone propionate), the cardiacglycoside digoxin, the alkaloid anti-migraine drug dihydroergotaminemesylate and other alkaloid ergotamines, the alkaloid bromocriptine usedin the treatment of Parkinson's disease, sumatriptan, rizatriptan,naratriptan, frovatriptan, almotriptan, zolmatriptan, morphine and themorphine analogue fentanyl (e.g., fentanyl citrate), glibenclamide (asulphonyl urea), benzodiazepines such as valium, triazolam, alprazolam,midazolam and clonazepam (typically used as hypnotics, for example totreat insomnia or panic attacks), the anti-psychotic agent risperidone,apomorphine for use in the treatment of erectile dysfunction, theanti-infective amphotericin B, the antibiotics tobramycin, ciprofloxacinand moxifloxacin, nicotine, testosterone, the anti-cholenergicbronchodilator ipratropium bromide, the bronchodilator formoterol,monoclonal antibodies and the proteins LHRH, insulin, human growthhormone, calcitonin, interferon (e.g., β- or γ-interferon), EPO andFactor VIII, as well as in each case pharmaceutically acceptable salts,esters, analogues and derivatives (for instance prodrug forms) thereof.

Additional examples of active agents suitable for practice with thepresent invention include but are not limited to aspariginase, amdoxovir(DAPD), antide, becaplerm in, calcitonins, cyanovirin, denileukindiftitox, erythropoietin (EPO), EPO agonists (e.g., peptides from about10-40 amino acids in length and comprising a particular core sequence asdescribed in WO 96/40749), dornase alpha, erythropoiesis stimulatingprotein (NESP), coagulation factors such as Factor Vila, Factor VIII,Factor IX, von Willebrand factor; ceredase, cerezyme, alpha-glucosidase,collagen, cyclosporin, alpha defensins, beta defensins, exedin-4,granulocyte colony stimulating factor (GCSF), thrombopoietin (TPO),alpha-1 proteinase inhibitor, elcatonin, granulocyte macrophage colonystimulating factor (GMCSF), fibrinogen, filgrastim, growth hormones,growth hormone releasing hormone (GHRH), GRO-beta, GRO-beta antibody,bone morphogenic proteins such as bone morphogenic protein-2, bonemorphogenic protein-6, OP-1; acidic fibroblast growth factor, basicfibroblast growth factor, CD-40 ligand, heparin, human serum albumin,low molecular weight heparin (LMWH), interferons such as interferonalpha, interferon beta, interferon gamma, interferon omega, interferontau; interleukins and interleukin receptors such as interleukin-1receptor, interleukin-2, interluekin-2 fusion proteins, interleukin-1receptor antagonist, interleukin-3, interleukin-4, interleukin-4receptor, interleukin-6, interleukin-8, interleukin-12, interleukin-13receptor, interleukin-17 receptor; lactoferrin and lactoferrinfragments, luteinizing hormone releasing hormone (LHRH), insulin,pro-insulin, insulin analogues (e.g., mono-acylated insulin as describedin U.S. Pat. No. 5,922,675), amylin, C-peptide, somatostatin,somatostatin analogs including octreotide, vasopressin, folliclestimulating hormone (FSH), influenza vaccine, insulin-like growth factor(IGF), insulintropin, macrophage colony stimulating factor (M-CSF),plasminogen activators such as alteplase, urokinase, reteplase,streptokinase, pamiteplase, lanoteplase, and teneteplase; nerve growthfactor (NGF), osteoprotegerin, platelet-derived growth factor, tissuegrowth factors, transforming growth factor-1, vascular endothelialgrowth factor, leukemia inhibiting factor, keratinocyte growth factor(KGF), glial growth factor (GGF), T Cell receptors, CDmolecules/antigens, tumor necrosis factor (TNF), monocytechemoattractant protein-1, endothelial growth factors, parathyroidhormone (PTH), glucagon-like peptide, somatotropin, thymosin alpha 1,thymosin alpha 1 IIb/IIIa inhibitor, thymosin beta 10, thymosin beta 9,thymosin beta 4, alpha-1 antitrypsin, phosphodiesterase (PDE) compounds,VLA-4 (very late antigen-4), VLA-4 inhibitors, bisphosponates,respiratory syncytial virus antibody, cystic fibrosis transmembraneregulator (CFTR) gene, deoxyreibonuclease (Dnase),bactericidal/permeability increasing protein (BPI), and anti-CMVantibody.

Exemplary monoclonal antibodies include etanercept (a dimeric fusionprotein consisting of the extracellular ligand-binding portion of thehuman 75 kD TNF receptor linked to the Fc portion of IgG1), abciximab,afeliomomab, basiliximab, daclizumab, infliximab, ibritumomab tiuexetan,mitumomab, muromonab-CD3, iodine 131 tositumomab conjugate, olizumab,rituximab, and trastuzumab (herceptin), am ifostine, am iodarone,aminoglutethimide, amsacrine, anagrelide, anastrozole, asparaginase,anthracyclines, bexarotene, bicalutamide, bleomycin, buserelin,busulfan, cabergoline, capecitabine, carboplatin, carmustine,chlorambucin, cisplatin, cladribine, clodronate, cyclophosphamide,cyproterone, cytarabine, camptothecins, 13-cis retinoic acid, all transretinoic acid; dacarbazine, dactinomycin, daunorubicin, dexamethasone,diclofenac, diethylstilbestrol, docetaxel, doxorubicin, epirubicin,estramustine, etoposide, exemestane, fexofenadine, fludarabine,fludrocortisone, fluorouracil, fluoxymesterone, flutamide, gemcitabine,epinephrine, L-Dopa, hydroxyurea, idarubicin, ifosfamide, imatinib,irinotecan, itraconazole, goserelin, letrozole, leucovorin, levamisole,lomustine, mechlorethamine, medroxyprogesterone, megestrol, melphalan,mercaptopurine, methotrexate, metoclopramide, mitomycin, mitotane,mitoxantrone, naloxone, nicotine, nilutamide, octreotide, oxaliplatin,pamidronate, pentostatin, pilcamycin, porfimer, prednisone,procarbazine, prochlorperazine, ondansetron, raltitrexed, sirolimus,streptozocin, tacrolimus, tamoxifen, temozolomide, teniposide,testosterone, tetrahydrocannabinol, thalidomide, thioguanine, thiotepa,topotecan, tretinoin, valrubicin, vinblastine, vincristine, vindesine,vinorelbine, dolasetron, granisetron; formoterol, fluticasone,leuprolide, midazolam, alprazolam, amphotericin B, podophylotoxins,nucleoside antivirals, aroyl hydrazones, sumatriptan; macrolides such aserythromycin, oleandomycin, troleandomycin, roxithromycin,clarithromycin, davercin, azithromycin, flurithromycin, dirithromycin,josamycin, spiromycin, midecamycin, leucomycin, miocamycin, rokitamycin,andazithromycin, and swinolide A; fluoroquinolones such asciprofloxacin, ofloxacin, levofloxacin, trovafloxacin, alatrofloxacin,moxifloxicin, norfloxacin, enoxacin, grepafloxacin, gatifloxacin,lomefloxacin, sparfloxacin, temafloxacin, pefloxacin, am ifloxacin,fleroxacin, tosufloxacin, prulifloxacin, irloxacin, pazufloxacin,clinafloxacin, and sitafloxacin; am inoglycosides such as gentamicin,netilmicin, paramecin, tobramycin, amikacin, kanamycin, neomycin, andstreptomycin, vancomycin, teicoplanin, rampolanin, mideplanin, colistin,daptomycin, gramicidin, colistimethate; polymixins such as polymixin B,capreomycin, bacitracin, penems; penicillins includingpenicllinase-sensitive agents like penicillin G, penicillin V;penicllinase-resistant agents like methicillin, oxacillin, cloxacillin,dicloxacillin, floxacillin, nafcillin; gram negative microorganismactive agents like ampicillin, amoxicillin, and hetacillin, cillin, andgalampicillin; antipseudomonal penicillins like carbenicillin,ticarcillin, aziocillin, meziocillin, and piperacillin; cephalosporinslike cefpodoxime, cefprozil, ceftbuten, ceftizoxime, ceftriaxone,cephalothin, cephapirin, cephalexin, cephradrine, cefoxitin,cefamandole, cefazolin, cephaloridine, cefaclor, cefadroxil,cephaloglycin, cefuroxime, ceforamide, cefotaxime, cefatrizine,cephacetrile, cefepime, cefixime, cefonicid, cefoperazone, cefotetan,cefinetazole, ceftazidime, loracarbef, and moxalactam, monobactams likeaztreonam; and carbapenems such as imipenem, meropenem, pentamidineisethiouate, albuterol sulfate, lidocaine, metaproterenol sulfate,beclomethasone diprepionate, triamcinolone acetamide, budesonideacetonide, fluticasone, ipratropium bromide, flunisolide, cromolynsodium, and ergotamine tartrate; taxanes such as paclitaxel; SN-38, andtyrphostines.

The above exemplary biologically active agents are mean to encompass,where applicable, analogues, agonists, antagonists, inhibitors, isomers,and pharmaceutically acceptable salt forms thereof. In reference topeptides and proteins, the invention is intended to encompass synthetic,recombinant, native, glycosylated, non-glycosylated, and biologicallyactive fragments and analogs thereof.

Drugs for which an immediate release into the bloodstream (i.e., rapidonset of pharmaceutical effect) might be particularly desirable includethose for use in the treatment of migraine, nausea, insomnia, allergic(including anaphylactic) reactions, neurological or psychiatricdisorders (in particular panic attacks and other psychoses or neuroses),erectile dysfunction, diabetes and related disorders and cardiacdisorders, anti-convulsants, bronchodilators and drugs for thealleviation of pain or inflammation.

The active substance may comprise two or more substances formulatedtogether, such as one coated with another, or one dispersed within amatrix of another, or a blend of two or more active substances. Commonexamples of such formulations include pharmaceutically active substancescoated with excipients, or solid dispersions of pharmaceutically activesubstances with excipients, the excipient often being present to modifythe release rate and/or to target delivery of the pharmaceutical.However, in general the active substances of the invention will exhibitthe improved flocculation behavior in the absence of excipients, i.e.,in the form of the active substance alone (for example, in the form ofpharmaceutically or nutraceutically active substance(s) withoutexcipients).

A third aspect of the present invention provides an active substance inparticulate form, which is insoluble in the fluid vehicle1,1,1,2-tetrafluoroethane (HFA 134a) and which when suspended in thatvehicle at a concentration of from 0.2% to 5% w/v exhibits aflocculation volume after 5 minutes which is at least 20% higher,preferably at least 50% or 150% or 200% or 250% higher, than thatexhibited by the same chemical entity having the same or a similarparticle size (typically measured MMAD, “similar” here meaning within80% to 120%, preferably within 90% to 110%, of the measured MMAD) butprepared using a micronization process.

A fourth aspect provides an active substance in particulate form, whichis insoluble in the fluid vehicle 1,1,1,2,3,3,3-heptafluoropropane (HFA227ea) and which when suspended in that vehicle at a concentration offrom 0.2% to 5% w/v exhibits a flocculation volume after 5 minutes whichis at least 20% higher, preferably at least 50% or 150% or 200% or 250%higher, than that exhibited by the same chemical entity having the sameor a similar particle size (as described above) but prepared using amicronization process.

By “micronization” in this context is meant a process involvingmechanical means, for instance milling or grinding, to reduce particlesize to the micrometer range.

According to the third and/or fourth aspects of the invention, theactive substance preferably exhibits this flocculation behavior after 6minutes, more preferably after 8 minutes, still more preferably after 10minutes, most preferably after 15, 30 or 60 minutes or in some casesafter 2, 6, 12 or even 24 hours. It may exhibit this behavior after only4, 3, 2 or in some cases 1 minute. The flocculation volume is preferablymeasured at a concentration of above 0.5% w/v, more preferably from 0.5to 3 or 4% w/v, most preferably from 0.5 to 1.5 or 2% w/v or from 0.8 to1.3 or 1.5% w/v, such as 1% w/v. The above described flocculationperformance may also be exhibited at lower active substanceconcentrations, for instance down to 0.15 or even 0.1% w/v.

Again, the active substance preferably exhibits this flocculationperformance in other nonsolvent fluid vehicles, in particularhydrofluorocarbon propellants.

A fifth aspect of the present invention provides an active substance inparticulate form, which is insoluble in the fluid vehicle1,1,1,2-tetrafluoroethane (HFA 134a) and which when suspended in thatvehicle at a concentration of from 0.2 to 5% w/v exhibits a rate ofchange (decrease) in flocculation volume, during the first 60 secondsafter thorough mixing of the active substance and vehicle, of 20% perminute or less.

A sixth aspect provides an active substance in particulate form, whichis insoluble in the fluid vehicle 1,1,1,2,3,3,3-heptafluoropropane (HFA227ea) and which when suspended in that vehicle at a concentration offrom 0.2 to 5% w/v exhibits a rate of change (decrease) in flocculationvolume, during the first 60 seconds after thorough mixing of the activesubstance and vehicle, of 20% per minute or less.

According to the fifth and/or sixth aspects of the invention, the rateof change in flocculation volume is preferably 15% per minute or less,more preferably 10% per minute or less, most preferably 5 or 3% perminute or less. Preferably it is within the quoted ranges for the first90 or 120 seconds after thorough mixing of the active substance andvehicle; certainly it is within those ranges during the first 30seconds.

Other preferred features of the active substances of the third to thesixth aspects of the invention, including the manner in which (andconcentration at which) their flocculation volumes may be measured, maybe as described for those of the first and second aspects.

When formulated in fluid suspensions, the active substances of thepresent invention can benefit from generally improved stability, inparticular relative to their micronized equivalents, during medium tolong term storage (for instance, for periods of a week or more,preferably a month or more, most preferably 3 or 6 or 12 or 18 or 24 or30 or even 36 months or more). They appear to remain more homogeneouslydispersed for longer periods of time. They also typically show a reducedtendency for particle growth and agglomeration in fluid suspensions, forexample, their MMADs may vary by no more than 30%, preferably no morethan 20% or 10%, of the starting value during storage as a fluidsuspension for a period of a week or more, preferably a month or more,most preferably 3 or 6 or 12 or 18 or 24 or 30 or even 36 months ormore. Again the fluid in which, and concentration at which, they aresuspended may be as described above in connection with the first to thesixth aspects of the invention; the fluid is preferably either HFA 134a,HFA 227ea, or a mixture thereof.

Thus, when used in aerosol formulations for use in inhalers (inparticular MDIs), the active substances of the invention can give a moreuniform dosing rate throughout the useable life of the inhaler. They canalso provide, in this context, greater uniformity in the efficacy of thedelivered drug throughout the inhaler life, particle size being relevantto bioavailability and to efficiency of delivery through the lung (inparticular the deep lung).

A typical aerosol canister, for example as used in a metered doseinhaler, can often allow the ingress of atmospheric moisture through itsdelivery mechanism during medium to long term storage. This moisture canreduce the stability of the suspension inside the canister. The activesubstances of the present invention can be significantly more stablethan for instance their micronized equivalents under such storageconditions, being less susceptible to particle growth and agglomerationeven in the presence of moisture. It has been found that even amorphousphase active substances according to the invention can be relativelystable under such conditions, despite the fact that moisture wouldnormally be expected to induce re-crystallization.

The stability of the active substances of the invention is therefore ofparticular use in aerosol formulations in delivery devices such asinhalers, in particular metered dose inhalers. Thus, when an activesubstance according to the invention is suspended in a fluid vehicle,suitably an aerosol propellant such as HFA 134a or HFA 227ea or amixture thereof, and delivered in a succession of doses of equal volumeusing a metered dose inhaler or into a measuring device such as acascade impactor (e.g., an ANDERSEN™ cascade impactor or a similar typeof cascade impactor).

a) the relative standard deviation RSD (i.e., the standard deviationexpressed as a percentage of the mean value) in the quantity of activesubstance delivered in each dose is preferably no more than 15% over 3,more preferably over 5, most preferably over 10 or 30 or 50 or 70 or 100or 150 or 200 successive doses. Yet more preferably, the RSD is no morethan 12 or 10 or 8 or 7 or 6 or 5 or 4 or even 3%.

b) the RSD in the fine particle content (the quantity of deliveredactive substance having a MMAD in the fine particle range, such as <3.5or 3.3 μm) of the delivered doses is preferably no more than 15% over 3,more preferably over 5, most preferably over 10 or 30 or 50 or 70 or 100or 150 or 200 successive doses. Yet more preferably, the RSD is no morethan 9 or 8 or 7 or 6 or 5 or even 2%.

c) the RSD in the fine particle fraction contained in each dose (i.e.,the quantity of active substance having a MMAD in the fine particlerange, expressed as a percentage of the total active substance contentin the relevant dose) is preferably no more than 17% over 3, morepreferably over 5, most preferably over 10 or 30 or 50 or 70 or 100 or150 or 200 successive doses. Yet more preferably, the RSD is no morethan 15 or 13 or 10 or 8 or 6 or 5%.

d) the RSD in the MMAD of the active substance particles contained ineach dose is preferably no more than 9.5% over 3, more preferably over5, most preferably over 10 or 30 or 50 or 70 or 100 or 150 or 200successive doses. Yet more preferably, the RSD is no more than 7 or 4 or3 or 2%.

e) the fine particle fraction contained in each dose is preferably atleast 25%, more preferably at least 26 or 27%, most preferably at least30 or even 35% over 3, more preferably over 5, most preferably over 10or 30 or 50 or 70 or 100 or 150 or 200 successive doses.

f) the MMAD of the particles delivered in each dose is preferably 4 μmor less, more preferably 3.8 or 3.5 μm or less, again suitably over 3,more preferably over 5, most preferably over 10 or 30 or 50 or 70 or 100or 150 or 200 successive doses.

For the purpose of measuring the properties (a) to (f) above, thedelivery or measuring device is ideally operated in the standard way,according to the manufacturer's instructions, which will typically forinstance involve agitating the aerosol formulation before deliveringeach dose. Suitable measurement methods are those described in Examples9 to 13 below, and typically involve the use of a cascade impactor suchas an ANDERSEN™ cascade impactor or a similar type of cascade impactor.For example, an aerosol can containing the formulation under test may becoupled to a cascade impactor via a standard adaptor and USP inductionport (“throat”), and the contents of the can dispensed into the impactorvia a conventional aerosol valve (typically crimped into the top of thecan) and actuator.

The relevant number of doses, over which the parameter in question ismeasured, may be delivered over a period of up to 1, 3, 6, 12, 18, 24 oreven 30 or 36 months, although under laboratory test conditions may bedelivered over a period of for instance from 30 minutes to 12 hours,more typically from 30 minutes to 4 or 5 hours, most typically from 2 to3 hours (e.g., with an interval of from 15 to 120 seconds, preferablyfrom 30 to 60 seconds, between doses). A suitable dose volume might befrom 20 to 100 μL, more typically from 45 to 70 μL such as from 50 to 65μL. Preferred features of the formulated suspensions, such as thevehicle type, the active substance concentration and the nature andquantity of additives (preferably none), may all be as described inconnection with the first to the sixth aspects of the invention.

For assessing performance over a larger number of doses (for example, 50or 100 or more), it may be sufficient to measure the relevantparameter(s) over a few (for instance from 2 to 6, preferably from 3 to5) successive doses at periods towards the start and end, and ideallyalso in the middle, of the total delivery period.

The RSD values referred to in (a) to (d) above are typically lower than(preferably at least 5% or 10% or 20% lower than) those obtained when amicronized form of the same chemical entity, having the same or asimilar MMAD, is subjected to the same test(s). In each case, uniformityof dosing characteristics is expected to be improved over any givenperiod of use by using an active substance in accordance with theinvention.

The active substances of the invention preferably exhibit theflocculation performance and/or stability described above when storedduring the relevant measurement period, in suspension in a fluid vehicle(whether or not within a delivery device such as an inhaler), at ambienttemperature (e.g., from 18 to 25° C., or from 20 to 23° C., such asabout 22° C., or at the accepted industrial standard temperature of 25°C.). More preferably, they exhibit that behavior and/or stability evenif subjected during the measurement period to fluctuations of up to ±5°C. or ±10° C. or ±15° C.

They may exhibit the above described flocculation performance and/orstability when their fluid suspensions are stored before or during therelevant measurement period at up to 20% or 30% or 40% or 60% or even75% relative humidity (RH). Higher storage temperatures and/orhumidities may be used, in conventional manner, to mimic longer termstorage periods, as may conventional thermal cycling procedures such asfreeze/thaw cycling. For example, storage for a given period at 40° C.and 75% RH is generally used to mimic storage for approximately 3 timesas long at 25° C. and 60% RH. Thermal cycling may for example involvecycling the storage temperature up to 2 or even 4 times daily, forinstance between 2° C. and 40° C. or (in the case of freeze/thawcycling) between −20° C. and 25° C. Measurements (for example, of MMADor fine particle fraction or dose content) may be taken both before andafter a period of storage under given conditions, or both before andafter thermal cycling, and the recorded values and RSDs between the twomeasurements or sets of measurements are preferably as described underpoints (a) to (f) above.

In certain cases, an active substance according to the present inventionmay be a pharmaceutically active substance or a pharmaceuticallyacceptable excipient (preferably a substance suitable for and/orintended for delivery by inhalation) other than salmeterol xinafoate(alone or co-formulated with hydroxypropyl cellulose); a-lactosemonohydrate; R-TEM P-lactamase; maltose; trehalose; sucrose; budesonide;salbutamol sulphate; nicotinic acid; paracetamol (alone or co-formulatedwith salmeterol xinafoate, L-poly(lactic acid), ethyl cellulose (EC),hydroxypropyl methyl cellulose (HPMC) or poly vinyl pyrrolidone (PVP));ibuprofen; ketoprofen (alone or co-formulated with EC, HPMC or PVP);salicylic acid; either indomethacin, carbamazepine, theophylline,ascorbic acid or a COX-2 selective inhibitor co-formulated with EC, HPMCor PVP; quinine sulphate co-formulated with EC; fluticasone propionate;omeprazole magnesium tetrahydrate; (S)-omeprazole magnesium trihydrate;formoterol fumarate dihydrate; felodipine; candesartan cilexetil;lysozyme (alone or co-formulated with sodium taurocholate); albumin;insulin (alone or co-formulated with sodium taurochlorate); terbutalinesulphate; fenoterol hydrobromide and/or ipratropium bromide.

It has been found that particulate active substances which exhibit theimproved flocculation behavior described in connection with the first tothe sixth aspects of this invention can be produced using the so-calledSEDS® (“Solution Enhanced Dispersion by Supercritical Fluid”) process(now known as the NEKTAR® SCF process), which is a version of the GASprocess referred to above.

Certain inhalation drugs have been produced before using SEDS®—see forexample WO-95/01221 (salmeterol xinafoate), WO-98/36825 (salbutamolsulphate), WO-98/52544 (budesonide) and WO-98/17676 (fluticasonepropionate). In the latter, some of the products are tested in a metereddose inhaler in the propellant HFA 134a, but flocculation volumes arenot measured or indeed mentioned and only relatively low drug/propellantconcentrations are used.

The NEKTAR® SCF process (SEDS®) is a process for forming particles of a“target” substance. It is a GAS process and so involves contacting asolution or suspension of the target substance in a fluid vehicle (the“target solution/suspension”) with a compressed fluid (generally asupercritical or near-critical fluid) anti-solvent under conditionswhich allow the anti-solvent to extract the vehicle from the targetsolution/suspension and to cause particles of the target substance toprecipitate from it. The conditions are such that the fluid mixtureformed between the anti-solvent and the extracted vehicle is still in acompressed (generally supercritical or near-critical) state. Theanti-solvent fluid should be a nonsolvent for the target substance andbe miscible with the fluid vehicle.

Carrying out a SEDS® process specifically involves using theanti-solvent fluid simultaneously both to extract the vehicle from, andto disperse, the target solution/suspension. In other words, the fluidsare contacted with one another in such a manner that the mechanical(kinetic) energy of the anti-solvent can act to disperse the targetsolution/suspension at the same time as it extracts the vehicle.“Disperse” in this context refers generally to the transfer of kineticenergy from one fluid to another, usually implying the formation ofdroplets, or of other analogous fluid elements, of the fluid to whichthe kinetic energy is transferred.

Suitable SEDS® processes are described in WO-95/01221, WO-96/00610,WO-98/36825, WO-99/44733, WO-99/59710, WO-01/03821, WO-01/15664,WO-02/38127 and WO-03/008082. Other suitable SEDS® processes aredescribed in WO-99/52507, WO-99/52550, WO-00/30612, WO-00/30613,WO-00/67892 and WO-02/058674, all of which are hereby incorporated intheir entirety by reference.

In SEDS®, the target solution/suspension and the anti-solvent arepreferably contacted with one another in the manner described inWO-95/01221 and/or WO-96/00610, being co-introduced into a particleformation vessel using a fluid inlet means which allows the mechanicalenergy (typically the shearing action) of the anti-solvent flow tofacilitate intimate mixing and dispersion of the fluids at the pointwhere they meet. The target solution/suspension and the anti-solventpreferably meet and enter the particle formation vessel at substantiallythe same point, for instance via separate passages of a multi-passagecoaxial nozzle.

Alternatively, the SEDS® process may be of the type described inWO-03/008082, in which the anti-solvent velocity as it enters theparticle formation vessel is near-sonic, sonic or supersonic and thetarget solution/suspension and the anti-solvent enter the vessel atseparate, although close, locations. Such a process is described forinstance in Example 1a below, in connection with the preparation ofsample B.

A particulate active substance according to the present invention ispreferably prepared using a GAS process, and more preferably using aSEDS® process, such as one or a combination of those described in theabove documents. Preferred features of the process may be as describedbelow in connection with the seventh aspect of the invention. The activesubstance may thus be insoluble or only sparingly soluble in water. Itis preferably insoluble or only sparingly soluble in compressed (e.g.,supercritical or near-critical) carbon dioxide. Such materials lendthemselves particularly well to SEDS® processing and indeed are oftendifficult to process using other particle formation techniques such asspray drying or freeze drying.

Although it is known that SEDS® can yield particulate products withcontrolled physicochemical characteristics such as particle size, sizedistribution and morphology, it has not previously been recognized thatproducts of the SEDS® process could exhibit such an improvement inflocculation performance compared to the corresponding substancesproduced by other particle formation techniques.

It is advantageous to be able to use the SEDS® process to achieve thisadditional improvement in product characteristics for materials whichneed to be delivered in suspension in a fluid vehicle. SEDS® is known togive the improved product properties described above, and in addition isa relatively efficient, safe, easily scalable, controlled andreproducible process. It can be used to prepare a wide range ofsubstances including water insoluble materials which cannot for instanceeasily be prepared by spray drying, materials which are insoluble insupercritical CO₂ which cannot easily be prepared by RESS, andtemperature- or otherwise-sensitive materials for which otherconventional particle formation processes might be inappropriate. SEDS®can also yield products which are highly crystalline in nature, and/orhigh in purity (including polymorphic purity) with low residual solventcontent.

Thus, a seventh aspect of the present invention provides the use of aSEDS® process, as described above, to produce an active substance inparticulate form, for the purpose of improving the flocculationperformance of the substance.

The process is preferably carried out using supercritical, near-criticalor liquid, more preferably supercritical, CO₂ as the anti-solvent. Thechoice of operating conditions such as temperature, pressure and fluidflow rates, and the choice of solvent and of anti-solvent modifier ifnecessary, will depend on the nature of the active substance, forinstance its solubility in the fluids present and, if it can exist indifferent polymorphic forms, which form is to be precipitated.Generally, the conditions should be chosen to minimize particlesizes—this will usually mean selecting a higher relative anti-solventflow rate (e.g., a target solution/suspension: anti-solvent flow rateratio (at or immediately prior to the two fluids coming into contactwith one another) of 0.03 or less, preferably 0.02 or less or even 0.01or less), and/or a higher operating temperature (e.g., from 50° C. to100° C., preferably from 70° C. to 90° C.), and/or a higher operatingpressure (e.g., from 80 to 210 bar, preferably from 90 to 200 bar).

The SEDS® processing conditions are also preferably selected to reduceresidual solvent levels and/or generally to increase the product purity(including if applicable its polymorphic purity). They may be selectedto increase the crystallinity of the product, in which case a lowerrelative anti-solvent flow rate may be preferred (for example, a targetsolution/suspension: anti-solvent flow rate ratio of 0.01 or greater,preferably 0.015 or 0.02 or greater) so as to slow down the solventextraction process.

The product of the seventh aspect of the invention is preferably aproduct according to one of the first to the sixth aspects.

“Improving the flocculation performance” in this context meansincreasing the flocculation volume exhibited by the substance in therelevant vehicle at a given concentration after a given period of time.It may include improving the performance (in particular, the uniformityin performance and/or storage stability) of fluid suspensions of theactive substance in delivery devices such as metered dose inhalers. TheSEDS® process is preferably used so as to achieve flocculation behavior,and/or stability, and/or performance in a delivery device, of the typesdescribed above in connection with the first, second, third, fourth,fifth and/or sixth aspects of the invention.

Such changes in performance and attributes may be as compared to thoseof the substance prior to the SEDS® processing, and/or of the samesubstance (preferably having the same particle size or a particle sizeno more than 10% or 20% different) when produced using another particleformation process such as micronizing or spray drying.

Flocculation volume, sometimes referred to as “sedimentation volume”,can be measured by a conventional and relatively simple method. Thesubstance under test, in particulate form, is suspended in the desiredfluid vehicle at a suitable concentration. The mixture should be wellagitated (typically, simply by shaking) to ensure a uniform dispersionof particles in the fluid at the start of measurement. Immediately afteragitation ceases, timing begins. The mixture is left to stand, usuallyunder ambient conditions, and the degree of settling or creaming of thesolid observed over time.

The flocculation volume of the mixture at a given point in time is thevolume of fluid which is still occupied by the particulate dispersion,expressed as a percentage of the total fluid volume. A higherflocculation volume thus indicates less settling/creaming, whichindicates improved performance.

All references herein to flocculation volumes, unless otherwise stated,are to measurements made at 22° C.

To achieve meaningful measurements of flocculation volume, the activesubstance should be insoluble in the chosen fluid vehicle, at least toan extent sufficient to allow suspension of the active substance assolid particles in the fluid. The solubility of the substance in thevehicle is preferably less than 10-5% w/v.

In certain active substance/vehicle systems, surfactants and/or otherdispersion enhancing or stabilizing additives may be used in order toachieve sufficient dispersion at the start of the test—these includemany systems in which the vehicle is water or another aqueous fluid.However, SEDS® products have been found to exhibit the desiredflocculation behavior even in the absence of such additives,particularly in non-aqueous vehicles.

According to an eighth aspect of the present invention, there isprovided an active substance for use in a method of surgery, therapy ordiagnosis practiced on a human or animal body, in which method thesubstance is delivered to a patient in suspension in a nonsolvent fluidvehicle in which the flocculation performance of the substance is asdefined above in relation to any one of the first to the sixth aspectsof the invention.

A ninth aspect of the invention provides the use of an active substancein the manufacture of a medicament which comprises a suspension of thatsubstance in a nonsolvent fluid vehicle, in which suspension theflocculation performance of the active substance is as defined above inrelation to any one of the first to the sixth aspects of the invention.The medicament may be for use in a method of surgery, therapy ordiagnosis practiced on a human or animal body, and is preferablysuitable for delivery by inhalation.

A tenth aspect provides the use of an active substance according to anyone of the first to the sixth aspects, in suspension in a nonsolventfluid vehicle at a concentration of at least 0.2% w/v, preferably atleast 0.5% w/v, and more preferably the suspension containing no, orless than 0.1% w/w based on the weight of the active substance,preferably less than 0.01% w/w or less than 0.001 or 0.0001% w/w,dispersion enhancing or stabilizing additives such as surfactants. Againthe suspension preferably contains no co-solvents or lubricity enhancingadditives.

For the eighth and ninth aspects of the invention, the active substanceis preferably an active substance according to one of the first to thesixth aspects. It is preferably a pharmaceutically active substance,more preferably one which is suitable for delivery by inhalation. Themedical method in which it may ultimately be used may involve thetreatment of any of the conditions mentioned in connection with theactive substances of the invention.

Other preferred features of the eighth to the tenth aspects of theinvention may be as described in connection with the first to the sixthaspects. In particular, the suspension is preferably an aerosolformulation in an aerosol propellant fluid, in particular in ahydrofluorocarbon propellant such as HFA 134a and/or HFA 227ea, and ispreferably suitable for delivery to a patient by inhalation.

An eleventh aspect of the invention provides a formulation, typically anaerosol formulation, containing an active substance according to any oneof the first to the sixth aspects suspended in a nonsolvent fluidvehicle.

The active substance is preferably a pharmaceutically active substance,although it may alternatively be a nutraceutical, a cosmetic or toiletryor any other active substance suitable for delivery in a nonsolventpropellant fluid.

The fluid vehicle is preferably an aerosol propellant fluid such asthose described above. It is preferably free of chlorofluorocarbonpropellants, and more preferably comprises a hydrofluorocarbonpropellant such as HFA 134a, HFA 227a, 1,1,2,2,3-pentafluoropropane or amixture of any thereof. Other suitable vehicles include other C1 to C4hydrofluorocarbons such as CHF2CHF2, CF3CH2F, CHF2CH3 and CF3CHFCF3, andperfluorocarbons such as CF3CF3 and CF3CF2CF3. The vehicle is preferablyof a pharmaceutically acceptable grade.

Most preferably the vehicle is HFA 134a, HFA 227a or a mixture thereof,such propellants are available, for instance, from DuPontFluoroproducts, Wilmington, Del. It may be water or another aqueousfluid, although the active substance should be insoluble in the chosenvehicle at least to an extent sufficient to allow its suspension assolid particles.

According to the present invention, a fluid vehicle may comprise amixture of two or more fluids. The mixture may be tailored for instanceto minimize the difference in densities between the vehicle and theactive substance and thus enhance the overall flocculation performanceof the active substance. As an example, a mixture of the propellants HFA134a and HFA 227a may be used to minimize the risk of either settling or“creaming” of a suspended active substance.

The concentration of the active substance in the formulation may be 0.1%w/v or greater, 0.2% w/v or greater, or even 0.5% w/v or 0.6% w/v or0.7% w/v or 0.8% w/v or 1% w/v or greater, depending on the dosing levelof the active substance. It is preferably from 0.1 or 0.2 to 5% w/v,more preferably from 0.5 or 0.7 to 1.6% w/v, most preferably from 0.5 or0.7 to 1.5 or 1.3 or 1.1 or 0.9% w/v, although it may be up to 3% w/v.In cases, therefore, the present invention can allow relatively highconcentration formulations to be prepared, of particular use for activesubstances which need to be delivered in high doses.

In cases however the concentration of the active substance in theformulation may be as low as 0.05 or 0.02% w/v.

The active substance generally need not be surface modified (e.g., bytreatment with a nonsolvent such as a non-polar liquid) prior toincorporation in the formulation.

One or more surfactants, or other dispersion enhancing or stabilizingadditives, may be included in the formulation, typical examples beingnonionic surfactants such as those available in the Tween™ series. Alubricant may be included to prevent the active substance depositing onthe internal surfaces of the aerosol can or other delivery device inwhich the formulation is to be used. Preferably, however, theformulation consists essentially of only the active substance and thevehicle, with only low levels (for instance, less than 0.1% w/w based onthe weight of the active substance, preferably less than 0.01% w/w orless than 0.001 or 0.0001% w/w) of, or more preferably in the absenceof, such additives. The formulation conveniently contains no, or onlylow levels (for instance, less than 0.01% w/w based on the weight of thefluid vehicle, preferably less than 0.001% w/w) of co-solvents, typicalco-solvents being alcohols such as ethanol.

The stability of the formulation is preferably as described above inconnection with the first to the sixth aspects of the invention, as isits aerosol performance (in particular dosage uniformity) in use in adelivery device such as a metered dose inhaler or when assessed forinstance using a cascade impactor. In particular, the formulationpreferably comprises a fine particle fraction (as defined above) of atleast 25%, more preferably at least 30%, most preferably 35%.

It has moreover been found that formulations according to the presentinvention can be particularly efficient for delivering active substancesto the central and in particular to the deep lung, and thus in turn forthe systemic delivery of active substances via the lung. Typicallyparticles with MMAD from 4 μm to 6 μm, more specifically from 4.7 μm to5.8 μm, will reach the “central” lung area (trachea and primary bronchi)whereas only those with MMAD of 3.5 μm, preferably 3.3 μm or less willpenetrate the “deep” lung region (alveoli, and secondary and terminalbronchi). The stability of the invented formulations, with respect toflocculation and aggregation of the suspended active substanceparticles, can allow them to deliver active substances having a highbioavailability and an efficient release profile.

Thus, when a formulation according to the invention is delivered to alive human or animal patient using a metered dose inhaler or anequivalent delivery device, the active substance may be released morerapidly into the patient's bloodstream, compared for instance to amicronized form of the same active substance (suitably having the sameor a similar MMAD) delivered under the same test conditions. Thebio-availability of the active substance (expressed for example as themaximum, or as the total plasma concentration attained following dosedelivery) may be higher than, preferably at least 1.5 or 1.8 or 2 or 2.5times as high as, that of the micronized equivalent. It has been foundthat active substances according to the invention may perform well insuch tests whether with or without excipients such as the polymericexcipients (e.g., polyvinyl pyrrolidone or polyethylene glycols)traditionally used to improve the bioavailability and/or release rate offor instance poorly water soluble drugs.

According to a preferred embodiment, a formulation according to theinvention may achieve a maximum concentration Cmax of the activesubstance in the patient's bloodstream within one hour of administration(typically of inhalation), preferably within 30 minutes, more preferablywithin 15 minutes of administration. This time to achieve maximumconcentration is referred to hereafter as T_(max).

Preferred features of the eleventh aspect of the invention, inparticular regarding the nature, particle size and/or morphology of theactive substance, and/or its stability and performance in a deliverydevice, may be as described in connection with the first to the tenthaspects.

The eleventh aspect of the invention may also encompass formulations inwhich the fluid (typically liquid) vehicle is other than an aerosolpropellant, for instance a liquid carrier for a pharmaceutically activesubstance intended for delivery by injection, orally or by any othersuitable administration route. The vehicle may be organic or aqueous, itmay comprise a mixture of two or more fluids, and it may includematerials other than the active substance.

A twelfth aspect of the present invention provides a drug deliverydevice, preferably an inhaler, which contains one or more dosageformulations of an active substance according to any one of the first tothe sixth aspects, and preferably also a suitable fluid vehicle in whichto aerosolize the substance. Alternatively, the delivery device maycontain, or be able to produce, one or more aerosol formulationsaccording to the eleventh aspect of the invention. The delivery deviceis preferably of the type designed to deliver a predetermined dose of anactive substance in a pressurized fluid vehicle, for instance a metereddose inhaler (which term includes pressurized metered dose inhalers(pMDIs)).

A thirteenth aspect of the invention provides an aerosol can containingan aerosol formulation according to the eleventh aspect of theinvention, and which is suitable for use in a delivery device such as aMDI, preferably a device according to the twelfth aspect of theinvention.

Because of the enhanced flocculation performance of the activesubstances of the invention, it may be unnecessary for the internalsurfaces of the aerosol can (i.e., those surfaces which come intocontact with the aerosol formulation during use) to be speciallytreated, for example with lubricity-enhancing coatings, to reduceretention of active substance deposits inside the can or its associateddelivery mechanisms.

The capacity of the aerosol can might typically be from 10 mL to 20 mL.It may suitably be made from toughened glass or aluminum. It maycomprise a conventional delivery mechanism, such as a metering valve oftypical volume 25 μL to 100 μL, more typically from 45 μL to 70 μL, suchas from 50 μL to 65 μL, together with a suitable valve actuator.

According to a fourteenth aspect, the invention provides a method fordelivering an active substance, the method involving charging an aerosolcan with an active substance and/or a formulation according to theinvention. Subsequent delivery of the can contents may be via a deliverydevice such as a MDI.

A fifteenth aspect provides a method of treatment of a human or animalpatient, which method involves administering to the patient, preferablyusing a method according to the fourteenth aspect of the invention, anactive substance and/or a formulation according to the invention.

Both of these methods preferably involve the use of a drug deliverydevice such as an inhaler, more preferably a delivery device accordingto the twelfth aspect of the invention. The active substance preferablycomprises a pharmaceutically active substance suitable for inhalationtherapy.

The present invention will now be described by way of example only andwith reference to the accompanying illustrative drawings.

EXAMPLES

In the following experiments, SEDS® processes were used to produce anumber of drugs in particulate form and their behavior in typical MDIpropellants was then examined.

In most cases the system used to carry out the particle formation was ofthe general type shown schematically in FIG. 1 of WO-95/01221. Atwo-passage coaxial nozzle (see FIG. 3 of WO-95/01221) was used toco-introduce into a 500 mL (except for Examples 1a) particle formationvessel (i) a solution of the drug in a solvent carrier and (ii)supercritical CO₂ as the anti-solvent. The anti-solvent extracted thecarrier at the nozzle outlet causing particles to be precipitated. Thetemperature and pressure were controlled within the vessel to ensure theCO₂ remained in supercritical form throughout the process, even whenmixed with the carrier.

The particulate products were all fine, free flowing powders with smoothparticle surfaces.

Flocculation volumes were measured in the general manner describedabove. 0.4 g of the relevant sample was filled into a 100 mL glassaerosol bottle. The bottle was pressurized with 40 mL of the propellantfluid to give a 1% w/v dispersion and then shaken vigorously for 30seconds to ensure complete dispersion of the powder. After agitation,the bottle was placed on a flat surface and the flocculation volumemeasured by eye every 15 seconds for the following 10 minutes.Measurements were taken at 22° C.

Example 1a Preparation of Salmeterol Xinafoate

Salmeterol xinafoate (sample A) in its polymorphic form I wasprecipitated from methanol (2% w/v) using an operating temperature of60° C., an operating pressure of 100 bar, a nozzle with a 200 μm outletdiameter, a particle formation vessel with 50 mL capacity, a salmeterolsolution flow rate of 0.4 m L/min and a CO₂ flow rate of 20 mL/min(note: all CO₂ flow rates were measured at the pump head). The producthad a MMAD of 5.3 μm (AEROSIZER™).

A further sample (B) of salmeterol xinafoate form I was made by amodified SEDS® process, as described in WO-03/008082, in which thesalmeterol solution and CO₂ were introduced through an inlet tube and aperpendicularly orientated nozzle (outlet diameter 200 μm) respectively,with a CO₂ flow rate sufficient for it to acquire a sonic velocity atthe nozzle outlet. For this particle formation process thesalmeterol/methanol solution concentration was 3% w/v, the operatingtemperature 36° C., the operating pressure 80 bar, the salmeterolsolution flow rate 4 mL/min and the CO₂ flow rate 158 mL/min. The CO₂was pre-heated to 90° C. prior to entering the nozzle, to compensate forJoule-Thomson cooling on expansion of the fluid across the nozzle. Theproduct had a MMAD of 1.6 μm (AEROSIZER™).

Example 1 b Flocculation Performance of Salmeterol Xinafoate

The flocculation performance of the products of Example 1a (samples Aand B) was tested in the propellants HFA 134a (less dense thansalmeterol xinafoate) and HFA 227ea (denser), in each case over a 10minute period. Also tested, under the same conditions, was a sample C ofsalmeterol xinafoate form I (MMAD 1.1 μm by AEROSIZER™) made by astandard micronization process.

FIG. 1 shows the time variation in flocculation volume of the threesamples in HFA 134a, expressed as a percentage of the initial volume.The performance of both SEDS® produced samples (i.e., products accordingto the present invention) was clearly superior to that of the micronizedsample, which after 3 minutes had a flocculation volume below 40% andafter 10 minutes of only 30%. The SEDS® samples retained, even after 10minutes, a flocculation volume of 90% or greater, in the case of sampleB greater than 98%.

Sample B was found to retain a flocculation volume of greater than 98%even after 24 hours standing.

The rate of change in flocculation volume for sample A, averaged overthe first 2 minutes standing, was −3% per minute. For sample B the rateof change was −0.2% per minute. For the micronized sample C, incontrast, the rate of change was −38% per minute averaged over the firstminute. These figures were derived by measuring flocculation volumesduring the relevant period and regressing them to a straight line togive an indication of the initial flocculation rate. The error incalculated flocculation rates is approximately 2.5% per minute; thus aflocculation rate of below 2.5% per minute may be equated withnegligible sedimentation or creaming.

FIG. 2 shows how the same samples performed in HFA 227ea. Again theperformance of the SEDS® produced samples A and B was superior to thatof the micronized sample C, which after 5 minutes had a flocculationvolume below 35%. The SEDS® samples retained a flocculation volume ofgreater than 40% after 5 and even 10 minutes.

In HFA 227ea, the rates of change in flocculation volume were −11% perminute for sample A and −19% per minute for sample B, both averaged overthe first 2 minutes. Sample C exhibited a flocculation rate of −53% perminute over the first minute.

Example 2a Preparation of Budesonide

Budesonide was precipitated from acetone (2% w/v) at 70° C. and 100 bar.The budesonide solution flow rate was 12.6 mL/min and the CO₂ flow rate833 mL/min. A nozzle with an 800 μm outlet was used. The product MMADwas 1.65 μm (AEROSIZER™).

Example 2b Flocculation Performance of Budesonide

The flocculation performance of the product of Example 2a was compared,in the propellants HFA 134a (less dense than budesonide) and HFA 227ea(denser), with that of a micronized budesonide sample (MMD 1.5 μm).

FIG. 3 shows the results in HFA 134a. Again the performance of theproduct of the invention was significantly better than that of themicronized sample, which after 2 minutes had a flocculation volume below40% and after 6 minutes of less than 30%. The SEDS® sample, even after10 minutes, still showed a flocculation volume of 80%. Its rate ofchange in flocculation volume was −3.5% per minute averaged over thefirst 2 minutes. The micronized sample exhibited a flocculation rate of−37% per minute over the first minute.

FIG. 4 shows the results in HFA 227ea, demonstrating significantlyhigher flocculation volumes for the SEDS® sample (greater than 50% after5 minutes and even after 10 minutes still greater than 40%) as comparedto the micronized one. Here the rate of change in flocculation volumefor the SEDS® sample was −13% per minute over the first 2 minutes, andfor the micronized sample 44% per minute over the first minute.

Example 3a Preparation of Fluticasone Propionate

Two samples of fluticasone propionate (in two different polymorphicforms I and II) were precipitated from acetone (4% w/v) using theoperating conditions set out in Table 1.

TABLE 1 CO₂ flow Solution Temperature Pressure rate flow ratePolymorphic MMD (μm) Sample (° C.) (bar) (ml/min) (ml/min) form(Sympatec ™) A 110 90 20 0.3 I 2.3 B 75 130 25 0.5 II 5.6 C 110 90 200.3 I 2.3

Example 3b Flocculation Performance of Fluticasone Propionate

Samples A and B from Example 3a were compared, in the propellant HFA134a (less dense than fluticasone propionate), with a micronized sampleD of fluticasone propionate form I (MMD 2.0 μm).

FIG. 5 shows the changes in flocculation volume of the three samplesover a 10 minute period, expressed as a percentage of the initialvolume. The performance of both SEDS® samples was significantly betterthan that of the micronized sample D, the latter having a flocculationvolume of below 30% after 10 minutes whereas the SEDS® products bothretained a flocculation volume of greater than 45% (in the case of the2.3 μm sample A, about 50%, and in the case of the 5.6 μm sample B,greater than 90%) after the same period.

It is notable that the micronized product, despite being smaller in sizethan both the SEDS® samples, still does not perform so well in thepropellant.

The rates of change in flocculation volume in HFA 134a were −20% perminute for sample A and −1% per minute for sample B, both averaged overthe first 2 minutes. Sample D exhibited a flocculation rate of −68% oper minute over the first minute.

The flocculation behavior of samples B and C from Example 3a was alsocompared with that of the micronized sample D in the propellant HFA227ea which is denser than fluticasone propionate. FIG. 6 shows theresults. Both SEDS® products exhibited a flocculation volume of greaterthan 90% even after 10 minutes, sample C performing particularly well,whereas the micronized sample had a flocculation volume of less than 30%after only 3 minutes. The flocculation rates were −0.5% per minute forsample B and 0% per minute for sample C, both averaged over the first 2minutes. Sample D exhibited a flocculation rate of −40% per minute overthe first minute.

Example 4a Preparation of Salbutamol Sulphate

Salbutamol sulphate was precipitated from methanol (1% w/v), usingdichloromethane (DCM) as an anti-solvent modifier. The operatingtemperature was 75° C., the pressure 200 bar. The salbutamol solutionflow rate was 42 m L/min, the DCM flow rate 84 mL/min and the CO₂ flowrate 633 mL/min. The nozzle used had a 900 μm diameter outlet.

The product was in the form of plate-like crystals with a MMD of 3.95 μm(SYMPATEC™).

Example 4b Flocculation Performance of Salbutamol Sulphate

The product of Example 4a was compared, in the propellants HFA 134a(less dense than salbutamol sulphate) and HFA 227ea (denser), with thatof a micronized salbutamol sample of MMD 14.5 μm.

FIG. 7 shows the changes in flocculation volume of the two samples inHFA 134a, over a 10 minute period, expressed as a percentage of theinitial volume. The product of the invention performed better than themicronized one, the latter having a flocculation volume of less than 20%after only 2 minutes whereas the SEDS® product retained a flocculationvolume greater than 70% over the 10 minute test period. The flocculationrates were −10% per minute for the SEDS® sample, averaged over the first2 minutes, and −84% per minute for the micronized sample, averaged overthe first minute.

FIG. 8 shows the results in HFA 227ea, in which the micronized samplehad a flocculation volume of less than 20% after only 2 minutes whereasthe SEDS® product still had a flocculation volume of greater than 70%after 8 minutes and greater than 60% after 10 minutes. The flocculationrates were −5% per minute for the SEDS® sample, averaged over the first2 minutes, and −55% per minute for the micronized sample, averaged overthe first minute.

Example 5a Preparation of Dihydroergotamine Mesylate

The polar drug dihydroergotamine mesylate (DHE) was precipitated frommethanol (5% w/v) at 50° C. and 100 bar. The DHE solution flow rate was1 mL/min and the CO₂ flow rate 200 mL/min. The process used was themodified SEDS® process used for salmeterol sample B in Example 1a, inwhich the CO₂ had a sonic velocity at the nozzle outlet and waspre-heated to 120° C. prior to entering the nozzle. The product had aMMAD of 1.25 μm (AEROSIZER™) and comprised small plate-like crystals.

Example 5b Flocculation Performance of Dihydroergotamine Mesylate

The flocculation behavior of the product of Example 5a was tested in thepropellant HFA 227ea, which is denser than DHE. Also tested was themicronized DHE starting material, which had a MMD of 15.1 μm.

FIG. 9 shows the results for the two samples, the SEDS® product clearlyperforming better than the micronized version. After 10 minutes, theSEDS® product still exhibited a 100% flocculation volume, whereas afteronly 1 minute the micronized sample had a flocculation volume of lessthan 20% and after 5 minutes of less than 10%. Even after 24 hoursstanding, the SEDS® sample still exhibited no visible creaming in theHFA 227ea.

The flocculation rates were 0% per minute for the SEDS® sample, averagedover the first 2 minutes, and −90% per minute for the micronized sample,averaged over the first minute.

Example 6a Preparation of Risperidone-(9-hydroxy)-palmitate

The polar drug risperidone-(9-hydroxy)-palmitate was precipitated fromtetrahydrofuran (5% w/v) at 80 bar. Two samples A and B were made usinga modified SEDS® process as for sample B of Example 1a (sonic velocityCO₂; CO₂ pre-heated to 90° C.; vessel temperature 36° C.); a thirdsample C was made using the process as for sample A of Example 1a, usingan operating temperature of 41° C. and a nozzle outlet diameter of 400μm. The risperidone solution flow rate was 4 mL/min for sample A and 1mL/min for samples B and C. The CO₂ flow rate was 200 mL/min in allexperiments.

The MMDs (SYMPATEC™) were 2.95 μm for sample A, 2.5 μm for sample B and3.5 μm for sample C.

Example 6b Flocculation Performance of Risperidone-(9-hydroxy)-palmitate

The products of Example 6a were compared with the starting material (MMD8.1 μm) in both HFA 134a and HFA 227ea.

In HFA 134a (FIG. 10), the Example 6a products clearly out-performed thestarting material, having in the case of samples A and B a flocculationvolume of 100% even after 10 minutes. Sample C still had a flocculationvolume of greater than 80% after 10 minutes, compared to the startingmaterial which after only 1 minute had a flocculation volume of lessthan 20%. The flocculation rates were 0, 0 and −1% per minute forsamples A, B and C respectively, averaged over the first 2 minutes, and−152% per minute for the micronized sample, averaged over the firstminute.

In HFA 227ea (FIG. 11), all the products of the invention exhibited aflocculation volume of greater than 80% after 5 minutes and greater than70% after 10 minutes. The starting material, in contrast, again had aflocculation volume of less than 20% after only 1 minute. Here theflocculation rates were −2.5, −3 and −3% per minute for samples A, B andC respectively, averaged over the first 2 minutes, and −117% per minutefor the micronized sample, averaged over the first minute.

Example 7a Preparation of “Compound I”

“Compound I”, an anti-asthma drug, was precipitated from methanol at 80°C. and 200 bar, using a 400 μm outlet nozzle. Two samples A and B weremade, using drug solution concentrations of 0.2 and 1.25% w/vrespectively. For preparing sample A, the drug solution flow rate was 10mL/min and the CO₂ flow rate 100 mL/min; for sample B the drug solutionflow rate was 4.5 mL/min and the CO₂ flow rate 150 mL/min. Needle-likecrystals were obtained in both cases; their MMDs (SYMPATEC™) were 5.7and 15.1 μm respectively.

Example 7b Flocculation Performance of Compound I

The products of Example 7a were compared with a micronized sample ofCompound I (MMD 3.4 μm) in both HFA 134a and HFA 227ea.

In HFA 134a (FIG. 12), the Example 7a products both retained aflocculation volume of 100% after 10 minutes, whereas the micronizedmaterial had a flocculation volume of less than 35% after the sameperiod. The flocculation rates were 0% per minute for samples A and B,both averaged over the first 2 minutes, and −23% per minute for themicronized sample, averaged over the first minute.

In HFA 227ea (FIG. 13), again the products of the present inventionexhibited no creaming during the 10 minute test period, whereas theflocculation volume of the micronized product had fallen to less than35% by the end of the test. The flocculation rates were again 0% perminute for samples A and B, averaged over the first 2 minutes.

Example 8a Preparation of Bromocriptine

Bromocriptine mesylate, a polar drug used in the treatment ofParkinson's disease, was precipitated from ethanol (concentration 1.2%w/v) using a modified SEDS® process as for sample B of Example 1a (sonicvelocity CO₂; CO₂ pre-heated to 90° C.). The operating pressure andtemperature were 80 bar and 36° C. respectively. The drug solution flowrate was 1 mL/min for sample A and 4 mL/min for sample B; in both casesthe CO₂ flow rate was 200 mL/min. The nozzle had a 200 μm outletdiameter.

Sample B precipitated in the form of small plate-like crystals, sample Awas amorphous.

Example 8b Flocculation Performance of Bromocriptine

The flocculation performance of the crystalline product (sample B) ofExample 8a was tested in both HFA 134a and HFA 227ea.

In HFA 134a, the sample retained a flocculation volume of 53% after 10minutes. In HFA 227ea, it still had a flocculation volume of 95% after10 minutes.

Examples 9 MDI Dosage Uniformity (DHE 0.65% w/w)

Crystalline DHE was prepared by the modified SEDS® process used forsalmeterol sample B in Example 1a. The drug was precipitated from adimethylformamide/water (9:1 v/v) mixture (5% w/v) at 50° C. and 100bar. The CO₂ had a sonic velocity at the nozzle outlet and waspre-heated to 112° C. prior to entering the nozzle. The nozzle had a 0.2mm outlet diameter and the particle formation vessel a capacity of 2 L.The CO₂ flow rate was 12 kg/hour, that for the DHE solution 1 mL/min.The product had the form of thin plate-like particles.

Aerosol formulations were then prepared in accordance with the inventionby suspending the DHE in the propellant HFA 134a (DuPont Fluoroproducts,Wilmington, Del.) in 18 mL aluminum pMDI aerosol canisters (Presspart,Cary, N.C.), at a drug concentration of 0.65% w/w. The canisters wereequipped with VALOIS™ DF 30/63 RCU 63 μL metering valves (ValoisPharmaceuticals, Marly-le-Roi, France). Note that in all aerosolperformance tests, unless otherwise specified, active substance sampleswere stored, formulated and tested under ambient conditions. Unit dosesof these formulations were delivered into an ANDERSEN™ cascade impactorfitted with a USP induction port and operated at 28.3 L/min. Theirdeposition profiles in the various stages of the impactor, and theirMMADs, were measured at the beginning (after priming −5 shots fired towaste) and end of the can life (approximately 100 shots), the aim beingto assess the dose uniformity over that period. Standard experimentalprocedures USP <601> and USP <905> were followed for the cascadeimpactor and dose content uniformity tests; DHE levels were assessed byHPLC and reported as ex-valve. The interval between shots was at least30 seconds, to prevent cooling of the aerosol can and consequentmoisture condensation.

Each formulation was tested in three aerosol cans. For each can and anygiven cascade impaction (CI) parameter (e.g., fine particle fractionFPF), a mean value was calculated from the start and end of test values.An overall mean, and the relative standard deviation (RSD) as apercentage of the mean, were also calculated based on all three cans.

The CI measurements and calculated values are shown in Table 2 for (a)the MMAD, (b) the fine particle dose (weight of delivered drug with MMAD<3.3 μm) and (c) the fine particle fraction FPF (percentage of delivereddrug particles with MMAD <3.3 μm).

The “% difference” is the difference between the start and end of testvalues expressed as a percentage of the mean.

TABLE 2 FPF Aerosol FPD (% < 3.3 μm) MMAD can Calculation (μg < 33 μm)ex actuator (μm) 1 Mean start/end 117.8 36.4 3.11 % difference 8.3 11.39.6 2 Mean start/end 106.6 34.8 3.22 % difference 0.7 9.8 4.0 3 Meanstart/end 113.9 40.4 2.69 % difference 0.4 12.9 1.9 Overall Mean all 3cans 112.8 37.2 3.00 % RSD 5.3 9.4 9.1

For all three parameters, in particular the fine particle dose, there isgood consistency between the start and end of test values, as well asrelatively little variation between the three cans. These data indicategood flocculation performance and (from the consistency in MMAD values)low levels of particle growth and aggregation, i.e., stable suspensionsof the drug in the propellant. The fine particle fractions and particlesizes make the DHE highly suitable for delivery by inhalation therapy,in particular for systemic delivery via the central lung.

Dose content uniformity was assessed using a Thiel apparatus followingthe USP method. Again three cans were tested. Measurements for total DHEcontent in the delivered dose were taken at the start, middle and end ofthe delivery period, corresponding approximately (after valve priming)to delivered doses 1, 50 and 100. Two priming shots were firedimmediately prior to collection of an analytical shot. Mean and % RSDvalues were calculated across these three measurements, for each can.

The results are shown in Table 3. All measurements (apart from the RSDpercentages) are in μg of delivered DHE.

TABLE 3 Aerosol can Start Middle End Mean % RSD 4 469.80 472.26 440.62460.89 3.82 5 453.98 372.45 407.79 411.41 9.94 6 419.26 397.08 465.15427.16 8.13

Again, the data show good uniformity in dose content over the testperiod, indicating good suspension stability.

Examples 10 MDI Dosage Uniformity (DHE 1.3% w/w)

Examples 9 were repeated but formulating the DHE in HFA 134a at aconcentration of 1.3% w/w. The results are shown in Tables 4 (CI tests)and 5 (dose content uniformity), and again demonstrate good suspensionstability and uniformity of delivery.

TABLE 4 FPF Aerosol FPD (% < 3.3 μm) MMAD can Calculation (μg < 3.3 μm)ex actuator (μm) 1 Mean start/end 167.9 26.1 3.595 % difference 0.4 6.14.2 2 Mean start/end 157.0 25.2 3.64 % difference 21.9 30.2 7.1 3 Meanstart/end 202.9 30.95 3.51 % difference 13.1 26.8 5.4 Overall Mean all 3cans 175.9 27.4 3.58 % RSD 14.5 16.5 3.6

TABLE 5 Aerosol can Start Middle End Mean % RSD 4 901.11 807.10 937.99882.07 7.65 5 813.66 864.35 797.93 825.31 4.21 6 899.94 839.24 770.06836.42 7.77

Examples 11 Formulation Stability (DHE)

The stability of aerosol formulations according to the invention wasassessed using a thermal cycling treatment designed to simulate a longerterm storage period under ambient conditions. Crystalline samples of thedrug DHE, prepared as described in Examples 9 (VMD 2.8 μm by SYMPATEC™;bulk powder density 0.14 g/mL), were suspended in HFA 134a in standardpMDI aerosol canisters, as in Examples 9 and 10. Two formulations wereprepared, 11A having a DHE concentration of 8 mg/mL and 11B a DHEconcentration of 16 mg/mL.

The canisters were subjected to temperature cycling consisting of three3 or 4 hour cycles between −20° C. and 40° C. for four weeks. Twosamples were removed at each of the 1, 2 and 4 week timepoints, andtested for particle size distribution (ANDERSEN™ cascade impaction(ACI), beginning of can life). Dose content uniformity (beginning,middle and end of can life) was assessed at the 1 and 4 week timepoints.The methodology was as in Examples 9. Three samples were also testedpre-thermal cycling (time zero); here particle sizes were assessed atboth the beginning and end (100th shot after priming) of the can life toobtain an average MMAD for all 6 measurements.

The particle size (ACI) results are shown in Table 6 for formulation 11Aand in Table 7 for formulation 11B. The fine particle fraction FPF isagain the fraction having MMAD <3.3 μm.

TABLE 6 FPF (%) (actuator + FPF (%) Actuator Oral dose MMAD throat +(ACI deposition (%) (throat + Time point (μm) ACI) only) (%) 0 + 1) 03.0 24.2 58.6 39.5 20.3 1 week  3.4 22.9 47.8 35.7 18.7 2 weeks 3.2 24.752.4 34.5 20.2 4 weeks 3.3 24.0 50.7 32.2 22.6

TABLE 7 FPF (%) (actuator + FPF (%) Actuator Oral dose MMAD throat +(ACI deposition (%) (throat + Time point (μm) ACI) only) (%) 0 + 1) 03.6 18.1 39.8 37.6 20.0 1 week  3.6 18.3 39.5 38.7 19.2 2 weeks 3.6 19.540.0 30.0 25.4 4 weeks 3.6 17.9 40.5 33.1 26.0

The data in Tables 6 and 7 demonstrate good MMAD and FPF consistencythroughout the thermal cycling, indicating a good degree of medium tolong term storage stability in the formulations of the invention. Fineparticle fractions are high and oro-pharyngeal depositions low.

The dose content uniformity results are shown in Tables 8 and 9 forformulations 11A and 11B respectively. Figures are for DHE dose contentsand for the % relative standard deviation (RSD) over the can life.

TABLE 8 Dose content Dose content Dose content (μg) (μg) (μg) Time pointbeginning middle end % RSD 0 447.7 413.9 437.9 4.0 1 week  513.1 496.6464.6 5.0 4 weeks 436.3 444.8 463.2 3.1

TABLE 9 Dose content Dose content Dose content (μg) (μg) (μg) Time pointbeginning middle end % RSD 0 871.6 836.9 835.3 2.4 1 week  981.8 869.2970.5 6.6 4 weeks 842.3 743.0 806.0 6.3

Again these data indicate good formulation stability, dose contentuniformity being preserved throughout the thermal cycling.

It is believed that the high crystallinity of the DHE of the inventioncontributes to its improved stability in aerosol formulations. Amorphousphase regions have a greater tendency to dissolve in a propellant fluidover time, particularly if (as often happens) atmospheric moistureenters the aerosol canister through the valve mechanism. Following thisdissolution, the active substance can then re-crystallize around thestill suspended particles, leading to particle growth and/or aggregationand a resultant change in the MMAD as well as in the ultimate aerosolperformance. The DHE formulations of the invention appear to have a highdegree of stability in this respect, even under conditions representingextended storage periods.

Examples 12 MDI Delivery Efficiency (Bromocriptine)

Amorphous and crystalline bromocriptine mesylate samples were preparedas described in Example 8a. Again sample A was amorphous and sample Bhighly crystalline.

Aerosol formulations 12A and 12B, containing the bromocriptine samples Aand B respectively suspended in HFA 227ea, were prepared in 19 mLaluminum aerosol canisters (Presspart Inc., Cary, N.C.) equipped with 50μL metering valves (Valois Pharmaceuticals, Marly-le-Roi, France). Thesuspension concentrations were 0.7% w/w for formulation 12A and 0.69%w/w for 12B. A control formulation 12C was prepared containing 0.74% w/wmicronized bromocriptine. In each case the powder was dispersed in thepropellant by first sonicating the canisters for 10-15 seconds in a bathsonicator and then placing them on a wrist-action shaker for about 30minutes. Each canister was then primed by wasting the first 5 shots.

The formulations were tested on an ANDERSEN™ cascade impactor todetermine their aerodynamic particle properties. The cascade impactorwas operated at 28.3 L/min and fitted with a USP induction port (<USP601> Pharmacopeial Previews 22, 3065 (1995)). The particle sizedistributions were fractionated into mass of drug deposited on the pMDIactuator, USP induction port, eight stages and terminal filter. Fiveshots were actuated per test, with an interval of at least 30 secondsbetween shots to prevent cooling of the can and resultant moisturecondensation. The bromocriptine content in each sample was determined byHPLC. The percentage of the total dose deposited from stage 4 to theterminal filter (corresponding to particles of MMAD less than 3.3 μm)was considered to be the fine particle fraction.

Measurements were recorded across (a) 5 shots delivered at the start ofthe experiment, after priming, (b) 5 shots in the middle of theexperiment and (c) 5 shots towards the end of the canister (total numberof shots per experiment approximately 120).

The tests for each of formulations 12A to 12C were conducted intriplicate, using three separate aerosol cans. A mean value wascalculated for each parameter, based on the nine measurements obtained(i.e., start, middle and end of test values for each of the three cans),together with the standard deviation SD.

The results are shown in Table 10. FPD is the fine particle dose and FPFthe fine particle fraction.

TABLE 10 FPD FPF MMAD Sample (μg < 3.3 μm) (% < 3.3 μm) (μm) 12A Mean180.48 38.41 3.26 SD 11.16 1.97 0.10 12B Mean 128.80 27.41 3.76 SD 9.601.47 0.06 12C Mean 104.17 21.84 3.89 SD 9.79 0.91 0.07

Generally speaking, in the tests involving formulations 12A and 12Baccording to the invention, extremely low variations (SD<3 for the FPF,and <0.2 for the MMAD) were seen between the start, middle and end oftest values recorded for each of the three cans. Overall, consistentlygood performance was observed for the formulations of the invention,which yielded fine aerosols with higher fine particle fractions anddecreased throat deposition as compared to the micronized control.

Examples 13 MDI Dosage Uniformity (Bromocriptine)

Dose content uniformity for the three formulations 12A to 12C, over theentire contents of the filled aerosol canisters, was further confirmedby subjecting them to a test protocol analogous to that used in Examples9. Using a baseplate (quadrapod) apparatus, from a 0.6 mm outsidediameter Valois boot actuator (Valois Pharmaceuticals, Marly-le-Roi,France), each formulation was actuated and collected into 10 mL ofmethanol/water. The bromocriptine content of each delivered dose wasdetermined in duplicate at the beginning, middle and end of each filledcanister, by HPLC analysis.

Table 11 shows the mean dose contents across three aerosol cans for eachformulation, determined at the start, middle and end of the can life.Also shown is the overall mean dose content for each formulation,together with the calculated % RSD which gives an indication of thevariation in dose content through the can life. Again all measurements(apart from the RSD percentages) are in μL of delivered drug.

TABLE 11 Overall Formulation Start Middle End average 12A Mean dose (μg)604.31 591.80 591.71 595.94 % RSD 2.28 2.37 3.64 2.84 12B Mean dose (μg)623.58 615.87 723.30 654.25 % RSD 4.62 7.10 12.66 11.64 12C Mean dose(μg) 662.02 612.65 672.53 649.07 % RSD 16.47 27.49 12.95 18.74

Again, the data for formulations 12A and 12B show good uniformity indose content over the test period, in particular compared to formulation12C containing the micronized drug. This indicates good suspensionstability for the formulations according to the invention. Even wherethe active substance is present in the amorphous phase, it appears tohave extremely good suspension stability in HFA 227ea, which in turnindicates improved stability against re-crystallization—this is thoughtto be due to increased purity, and in particular to reduced residualsolvent levels, when an active substance is prepared in accordance withthe invention as opposed to by a conventional route such ascrystallization followed by micronization.

1. An aerosol formulation containing a particulate active substancehaving a mass median aerodynamic diameter (MMAD) of less than 10 μm,suspended in a nonsolvent hydrofluorocarbon fluid vehicle at aconcentration of 0.5% w/v or greater.
 2. An aerosol formulationaccording to claim 1, wherein the particulate active substance has aMMAD of less than 5 μm.
 3. An aerosol formulation according to claim 1,wherein the concentration of the active substance in the vehicle is from0.5 to 1.5% w/v.
 4. An aerosol formulation according to claim 1, whereinthe fluid vehicle is either 1,1,1,2-tetrafluoroethane (HFA 134a) or1,1,1,2,3,3,3-heptafluoropropane (HFA 227ea) or a mixture thereof.
 5. Anaerosol formulation according to claim 4, wherein the active substanceis a pharmaceutically or nutraceutically active substance which issuitable for delivery by inhalation.
 6. An aerosol formulation accordingto claim 4, which contains no or substantially no dispersion enhancingor stabilizing additives or co-solvents or lubricity enhancingadditives.
 7. An aerosol formulation of claim 6, which is suitable foruse in a metered dose inhaler.
 8. An aerosol formulation of claim 4,which when delivered in a succession of equal volume doses using ametered dose inhaler, or when delivered in a succession of equal volumedoses into a cascade impactor, gives one or more of the followingresults: a) the relative standard deviation RSD (ie, the standarddeviation expressed as a percentage of the mean value) in the quantityof active substance delivered in each dose is no more than 15% over 100successive doses; b) the RSD in the fine particle content (the quantityof delivered active substance having a MMAD in the fine particle range,<3.5 μm) of the delivered doses is no more than 15% over 100 successivedoses; c) the RSD in the fine particle fraction contained in each dose(ie, the quantity of active substance having a MMAD in the fine particlerange, expressed as a percentage of the total active substance contentin the relevant dose) is no more than 17% over 100 successive doses; d)the RSD in the MMAD of the active substance particles contained in eachdose is no more than 9.5% over 100 successive doses; e) the fineparticle fraction contained in each dose is at least 25% over 100successive doses; f) the MMAD of the particles delivered in each dose is4 μm or less over 100 successive doses.
 9. An aerosol formulationaccording to claim 8, which gives one or more of the results (a) to (f)after storage at 25° C. and 60% relative humidity for a period of atleast 12 months.
 10. An aerosol formulation of claim 1, which whendelivered to a live human or animal patient using a metered dose inhaleror an equivalent delivery device, leads to a more rapid release of theactive substance into the patient's bloodstream than does a formulationcontaining, in the same fluid vehicle and at the same concentration, thesame chemical entity having the same or a similar particle size butproduced by micronisation.
 11. An aerosol formulation according to claim10, which when delivered to a live human or animal patient using ametered dose inhaler or an equivalent delivery device, leads to themaximum concentration, C_(max), of the active substance in the patient'sbloodstream being achieved within 30 minutes of delivery.
 12. An aerosolformulation according to claim 11, wherein C_(max) is achieved within 15minutes of delivery.
 13. An aerosol formulation according to claim 4,which when delivered to a live human or animal patient using a metereddose inhaler or an equivalent delivery device, yields a higher totaland/or maximum plasma concentration of the active substance in thepatient, following dose delivery, than does a formulation containing, inthe same fluid vehicle and at the same concentration, the same chemicalentity having the same or a similar particle size but produced bymicronisation.
 14. An aerosol formulation of claim 4, which exhibits aflocculation volume of 35% or greater 30 seconds after mixing of theactive substance and vehicle.
 15. An aerosol formulation according toclaim 14, which exhibits a flocculation volume in the relevant vehicleof 50% or greater 30 seconds after mixing.
 16. An aerosol formulationaccording to claim 14, wherein the defined flocculation volume isexhibited 5 minutes after mixing.
 17. An aerosol formulation accordingto claim 16, wherein the defined flocculation volume is exhibited 10minutes after mixing.
 18. An aerosol formulation of claim 4, whichexhibits a rate of change (decrease) in flocculation volume, during thefirst 60 seconds after thorough mixing of the active substance andvehicle, of 20% per minute or less.
 19. An aerosol formulation accordingto claim 18, which in the defined circumstances exhibits a rate ofchange (decrease) in flocculation volume, during the first 60 secondsafter thorough mixing of the active substance and vehicle, of 10% perminute or less.
 20. An aerosol formulation according to claim 18, whichin the defined circumstances exhibits a rate of change (decrease) inflocculation volume, during the first 120 seconds after thorough mixingof the active substance and vehicle, of 20% per minute or less.
 21. Anaerosol formulation according to claim 4, which exhibits a flocculationvolume, 5 minutes after mixing of the active substance and vehicle,which is at least 20% higher than that exhibited by a formulation, inthe same vehicle and at the same concentration, containing the samechemical entity having the same or a similar particle size but preparedusing a micronisation process.
 22. An aerosol formulation of claim 4,wherein the mass median aerodynamic diameter (MMAD) of the activesubstance particles is less than 3.5 μm.
 23. An aerosol formulation ofclaim 4, wherein the active substance is in the form of solid particles.24. An aerosol formulation of claim 23, wherein the active substance isin a crystalline form.
 25. An aerosol formulation according to claim 24,wherein the active substance has a crystalline form which issignificantly longer in one dimension than in at least one otherdimension.
 26. An aerosol formulation according to claim 23, wherein theactive substance contains less than 200 ppm residual solvent.
 27. Anaerosol formulation according to claim 26, wherein the active substancecomprises a drug for use in the treatment of a condition selected fromthe group consisting of migraine, nausea, insomnia, allergic (includinganaphylactic) reactions, neurological or psychiatric disorders, erectiledysfunction, diabetes and related disorders, cardiac disorders,convulsions, bronchial disorders, pain, inflammation and combinationsthereof.
 28. An aerosol formulation according to claim 4, wherein theactive substance has been prepared by contacting a solution orsuspension of the active substance in a fluid carrier (the “targetsolution/suspension”) with a compressed fluid anti-solvent, underconditions which allow the anti-solvent simultaneously both to extractthe fluid carrier from, and to disperse, the target solution/suspensionso as to cause particles of the active substance to precipitate from it.